1. Field of the Invention
The invention relates to a process for the coating of substrates with a silicon-containing protective layer by chemical vapour deposition (CVD) coating.
2. Description of the Prior Art
In order to protect high-temperature components of carbon from oxidation it is known to provide the component with a quartz glass (SiO.sub.2) layer by CVD using silanes. The amorphous quartz glass layer passes into the crystalline state (cristobalite) at a temperature above approximately 1,100.degree. C. This so-called transition of quartz leads to cracks in the coating which lead to rapid oxidation of the carbon component, in particular following cooling and re-heating of the component, that is to say under conditions of thermal shock stress.
Although cracking can be checked by applying further layers, for example of silicon carbide, such a sequence of different layers is associated with a corresponding number of process steps and is hence costly and time-consuming. Moreover, a quartz glass layer applied to a metal substrate by CVD leads to spalling under conditions of mechanical and thermal shock stress.
The object of the invention is to provide substrates of different types in simple manner with a firmly adhering protective layer which also withstands high thermal shock stresses.
This is achieved according to the invention as decribed below.